The present invention relates to methods for treating proteins to modify their foaming properties; to modified proteins, in particular whey proteins, produced by these methods; and to food products comprising modified proteins.
Whey is a by-product of the production of cheese. Traditionally, whey is disposed of as unused waste or used as fertilizer or animal feed. However, efforts are currently directed towards processing whey into commercially useful products.
The present invention relates to the modification of whey proteins by limited proteolysis to provide particularly beneficial foaming properties, allowing the modified proteins to be used in a variety of food applications.
U.S. Pat. No. 4,089,987 and Phillips et al., J. Food Sci. 55:1116, 1990, describe non-enzymatic methods for modifying whey proteins. Ju et al., J. Dairy Sci. 78:2119, 1995; Althouse et al., J. Food Sci. 60:1110, 1995; U.S. Pat. Nos. 4,427,658; 5,691,165; and 5,866,357; To et al., Can. Inst. Food Sci. Technol. J. 18:150, 1985; U.S. Pat. No. 5,035,902; and Mutilangi et al., J. Food Sci. 61:270, 1996, disclose proteolysis of whey proteins. Kuehler et al., J Food Sci 39: 370, disclose a moderate increase in foam volume of whey proteins caused by digestion with Pronase, which contains a glu-specific protease component (Breddam et al., Eur J Biochem 296: 103, 1992).
Thus, there is a need in the art for methods and compositions that provide whey proteins with superior foaming properties and other functional features.
The present invention encompasses methods for producing a high-foaming modified whey protein preparations, which are achieved by contacting an aqueous solution of a whey protein preparation with a protease under conditions that result in a degree of hydrolysis of between about 4 and about 10%, preferably between about 5 and about 8%, wherein the aqueous solution contains between about 15 and about 30% w/w whey protein dry solids, preferably about 20% dry solids. In preferred embodiments, the whey protein preparation contains at least about 3% fat by weight. The methods of the invention result in modified whey proteins that exhibit a foaming capacity, as measured by foaming overrun, that is at least about 2-fold, and preferably at least about 5-fold, better than the unmodified whey proteins from which they are derived.
In preferred embodiments, the protease is a glu/asp-specific protease, preferably derived from Bacillus and most preferably from B. licheniformis. 
In another aspect, the invention provides modified whey protein compositions that exhibit a foaming overrun of at least about 800%, preferably at least about 1200% and most preferably at least about 1500%, which are produced using the above-described methods from whey protein concentrates having a fat content of at least about 3%.
In another aspect, the invention provides food products that comprise the modified whey proteins described herein.